net: inet_add_protocol() can use cmpxchg()
Use cmpxchg() to get rid of spinlocks in inet_add_protocol() and
friends.
inet_protos[] & inet6_protos[] are moved to read_mostly section
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/protocol.c b/net/ipv4/protocol.c
index f2d2973..65699c2 100644
--- a/net/ipv4/protocol.c
+++ b/net/ipv4/protocol.c
@@ -28,8 +28,7 @@
#include <linux/spinlock.h>
#include <net/protocol.h>
-const struct net_protocol *inet_protos[MAX_INET_PROTOS] ____cacheline_aligned_in_smp;
-static DEFINE_SPINLOCK(inet_proto_lock);
+const struct net_protocol *inet_protos[MAX_INET_PROTOS] __read_mostly;
/*
* Add a protocol handler to the hash tables
@@ -37,20 +36,9 @@
int inet_add_protocol(const struct net_protocol *prot, unsigned char protocol)
{
- int hash, ret;
+ int hash = protocol & (MAX_INET_PROTOS - 1);
- hash = protocol & (MAX_INET_PROTOS - 1);
-
- spin_lock_bh(&inet_proto_lock);
- if (inet_protos[hash]) {
- ret = -1;
- } else {
- inet_protos[hash] = prot;
- ret = 0;
- }
- spin_unlock_bh(&inet_proto_lock);
-
- return ret;
+ return !cmpxchg(&inet_protos[hash], NULL, prot) ? 0 : -1;
}
EXPORT_SYMBOL(inet_add_protocol);
@@ -60,18 +48,9 @@
int inet_del_protocol(const struct net_protocol *prot, unsigned char protocol)
{
- int hash, ret;
+ int ret, hash = protocol & (MAX_INET_PROTOS - 1);
- hash = protocol & (MAX_INET_PROTOS - 1);
-
- spin_lock_bh(&inet_proto_lock);
- if (inet_protos[hash] == prot) {
- inet_protos[hash] = NULL;
- ret = 0;
- } else {
- ret = -1;
- }
- spin_unlock_bh(&inet_proto_lock);
+ ret = (cmpxchg(&inet_protos[hash], prot, NULL) == prot) ? 0 : -1;
synchronize_net();